Provided by: nasm_2.09.10-1_amd64 bug


       nasm - the Netwide Assembler, a portable 80x86 assembler


       nasm  [  -@  response  file ] [ -f format ] [ -o outfile ] [ -l listfile ] [ options...  ]
       nasm -h
       nasm -v


       The nasm command assembles the file filename and directs output to  the  file  outfile  if
       specified.  If  outfile is not specified, nasm will derive a default output file name from
       the name of its input file, usually by appending  `.o'  or  `.obj',  or  by  removing  all
       extensions for a raw binary file. Failing that, the output file name will be `nasm.out'.

       -@ filename
              Causes  nasm  to  process  options  from  filename  as if they were included on the
              command line.

       -a     Causes nasm to assemble the given input  file  without  first  applying  the  macro

       -D macro[=value]
              Pre-defines a single-line macro.

       -d macro[=value]
              Same as the -D option.

       -e     Causes  nasm to preprocess the given input file, and write the output to stdout (or
              the specified output file name), and not actually assemble anything.

       -f format
              Specifies the output file format. To see a list of valid output  formats,  use  the
              -hf option.

       -g     Causes nasm to generate debug information in selected format

       -h     Causes nasm to exit immediately, after giving a summary of its invocation options.

       -hf    Same as -h , but also lists all valid output formats.

       -I directory
              Adds  a directory to the search path for include files. The directory specification
              must include the trailing slash, as it will be directly prepended to  the  name  of
              the include file.

       -i directory
              Same as the -I option.

       -l listfile
              Causes  an assembly listing to be directed to the given file, in which the original
              source is displayed on the right hand side (plus the source for included files  and
              the  expansions of multi-line macros) and the generated code is shown in hex on the

       -M     Causes nasm to output Makefile-style  dependencies  to  stdout;  normal  output  is

       -MG file
              Same as -M but assumes that missing Makefile dependecies are generated and added to
              dependency list without a prefix.

       -MF file
              Output Makefile-style dependencies to the specified file.

       -MD file
              Same as a combination of -M and -MF options.

       -MT file
              Override the default name of the dependency target dependency target name. This  is
              normally the same as the output filename, specified by the -o option.

       -MQ file
              The  same  as  -MT except it tries to quote characters that have special meaning in
              Makefile syntax. This is not foolproof, as not all characters with special  meaning
              are quotable in Make.

       -MP    Emit phony target

       -O number
              Optimize branch offsets.
              -O0 :No optimization (default)
              -O1 :Minimal optimization
              -Ox :Multipass optimization (recommended)

       -o outfile
              Specifies  a  precise  name for the output file, overriding nasm's default means of
              determining it.

       -P file
              Specifies a file to be pre-included, before the  main  source  file  starts  to  be

       -p file
              Same as the -P option.

       -r     Causes nasm to exit immediately, after displaying its version number.  (obsolete)

       -s     Causes  nasm  to  send  its  error  messages  and/or help text to stdout instead of

       -t     Causes nasm to assemble in SciTech TASM compatible mode

       -U macro
              Undefines a single-line macro.

       -u macro
              Same as the -U option.

       -v     Causes nasm to exit immediately, after displaying its version number.

              Causes nasm to enable or disable certain classes of warning messages,  for  example
              -w+orphan-labels or -w-macro-params

       -X format
              specifies error reporting format (gnu or vc).

       -Z filename
              Causes  nasm to redirect error messages to filename.  This option exists to support
              operating systems on which stderr is not easily redirected.


              Prepend or append (respectively)  the  given  argument  to  all  global  or  extern

       This  man  page  does  not fully describe the syntax of nasm's assembly language, but does
       give a summary of the differences from other assemblers.

       Registers have no leading `%' sign, unlike gas, and  floating-point  stack  registers  are
       referred to as st0, st1, and so on.

       Floating-point  instructions  may  use  either the single-operand form or the double. A TO
       keyword is provided; thus, one could either write

                      fadd st0,st1
                      fadd st1,st0

       or one could use the alternative single-operand forms

                      fadd st1
                      fadd to st1

       Uninitialised storage is reserved using the RESB, RESW, RESD, RESQ, REST and RESO  pseudo-
       opcodes,  each  taking  one parameter which gives the number of bytes, words, doublewords,
       quadwords or ten-byte words to reserve.

       Repetition of data items is not done by the DUP keyword as seen in DOS assemblers, but  by
       the use of the TIMES prefix, like this:

             message: times 3 db 'abc'
                      times 64-$+message db 0

       which  defines  the string `abcabcabc', followed by the right number of zero bytes to make
       the total length up to 64 bytes.

       Symbol references are always understood to be immediate (i.e. the address of the  symbol),
       unless  square  brackets  are  used, in which case the contents of the memory location are
       used. Thus:

                      mov ax,wordvar

       loads AX with the address of the variable `wordvar', whereas

                      mov ax,[wordvar]
                      mov ax,[wordvar+1]
                      mov ax,[es:wordvar+bx]

       all refer to the contents of memory locations. The syntaxes

                      mov ax,es:wordvar[bx]
                      es mov ax,wordvar[1]

       are not legal at all, although the use of a segment register name as an instruction prefix
       is  valid,  and  can be used with instructions such as LODSB which can't be overridden any
       other way.

       Constants may be expressed numerically in most formats: a trailing H, Q or B denotes  hex,
       octal or binary respectively, and a leading `0x' or `$' denotes hex as well. Leading zeros
       are not treated specially at all.  Character constants may be enclosed in single or double
       quotes;  there  is  no escape character. The ordering is little-endian (reversed), so that
       the character constant 'abcd' denotes 0x64636261 and not 0x61626364.

       Local labels begin with a period,  and  their  `locality'  is  granted  by  the  assembler
       prepending the name of the previous non-local symbol. Thus declaring a label `.loop' after
       a label `label' has actually defined a symbol called `label.loop'.

       SECTION name or SEGMENT name causes nasm  to  direct  all  following  code  to  the  named
       section.  Section  names  vary  with output file format, although most formats support the
       names .text, .data and .bss.  (The exception is the obj format, in which all segments  are

       ABSOLUTE  address  causes  nasm  to  position  its  notional assembly point at an absolute
       address: so no code or data may be generated, but you can use RESB, RESW and RESD to  move
       the assembly point further on, and you can define labels. So this directive may be used to
       define data structures. When you have finished doing absolute  assembly,  you  must  issue
       another SECTION directive to return to normal assembly.

       BITS  16,  BITS  32  or  BITS  64  switches  the  default processor mode for which nasm is
       generating code: it is equivalent to USE16 or USE32 in DOS assemblers.

       EXTERN symbol and GLOBAL symbol import and export symbol definitions,  respectively,  from
       and  to other modules. Note that the GLOBAL directive must appear before the definition of
       the symbol it refers to.

       STRUC strucname and ENDSTRUC, when used to bracket a  number  of  RESB,  RESW  or  similar
       instructions,  define  a  data  structure.  In  addition  to  defining  the offsets of the
       structure members, the construct also defines a symbol for  the  size  of  the  structure,
       which is simply the structure name with _size tacked on to the end.

       ORG  address  is used by the bin flat-form binary output format, and specifies the address
       at which the output code will eventually be loaded.

       GROUP grpname seg1 seg2...  is used by the  obj  (Microsoft  16-bit)  output  format,  and
       defines  segment  groups. This format also uses UPPERCASE, which directs that all segment,
       group and symbol names output to the object file should be in  uppercase.  Note  that  the
       actual assembly is still case sensitive.

       LIBRARY  libname  is  used  by the rdf output format, and causes a dependency record to be
       written to the output file which indicates that the program requires a certain library  in
       order to run.

       Single-line  macros  are  defined  using  the  %define  or %idefine commands, in a similar
       fashion to the  C  preprocessor.  They  can  be  overloaded  with  respect  to  number  of
       parameters,  although  defining  a macro with no parameters prevents the definition of any
       macro with the same name taking parameters, and vice versa.  %define defines macros  whose
       names match case-sensitively, whereas %idefine defines case-insensitive macros.

       Multi-line  macros  are  defined  using %macro and %imacro (the distinction is the same as
       that between %define and %idefine), whose syntax is as follows:

             %macro name minprm[-maxprm][+][.nolist] [defaults]
                      <some lines of macro expansion text>

       Again, these macros  may  be  overloaded.  The  trailing  plus  sign  indicates  that  any
       parameters  after  the  last one get subsumed, with their separating commas, into the last
       parameter. The defaults part can  be  used  to  specify  defaults  for  unspecified  macro
       parameters after minparam.  %endm is a valid synonym for %endmacro.

       To  refer  to the macro parameters within a macro expansion, you use %1, %2 and so on. You
       can also enforce that a macro parameter should contain a condition code by using %+1,  and
       you can invert the condition code by using %-1.  You can also define a label specific to a
       macro invocation by prefixing it with a double % sign.

       Files can be included using the %include directive, which works like C.

       The preprocessor has a  `context  stack',  which  may  be  used  by  one  macro  to  store
       information  that  a  later  one  will retrieve. You can push a context on the stack using
       %push, remove one using %pop, and change the name of the top context  (without  disturbing
       any  associated  definitions)  using %repl.  Labels and %define macros specific to the top
       context may be defined by prefixing their names with %$, and things specific to  the  next
       context down with %$$, and so on.

       Conditional  assembly  is  done  by  means  of  %ifdef, %ifndef, %else and %endif as in C.
       (Except that %ifdef can accept several putative macro names, and will evaluate TRUE if any
       of  them  is  defined.)  In  addition,  the  directives  %ifctx and %ifnctx can be used to
       condition on the name of the top context on the context stack. The obvious set  of  `else-
       if' directives, %elifdef, %elifndef, %elifctx and %elifnctx are also supported.


       Please report bugs through the bug tracker function at


       as(1), ld(1).

                                  The Netwide Assembler Project                           NASM(1)